1. Field of the Invention
The present invention relates to a semiconductor device which includes a circuit including a semiconductor element such as a transistor. For example, the present invention relates to a power device which is mounted on a power supply circuit; a semiconductor integrated circuit including a memory, a thyristor, a converter, an image sensor, or the like; and an electro-optical device typified by a liquid crystal display panel; a light-emitting display device including a light-emitting element; and an electronic device including any of the above as a component.
In this specification, a semiconductor device generally refers to a device which can function by utilizing semiconductor characteristics; an electro-optical device, a light-emitting display device, a semiconductor circuit, and an electronic device are all included in the category of the semiconductor device.
2. Description of the Related Art
Many transistors formed over a glass substrate or the like are manufactured using amorphous silicon, polycrystalline silicon, or the like, as typically seen in liquid crystal display devices. Although transistors including amorphous silicon have low field-effect mobility, they can be formed over a larger glass substrate. On the other hand, although transistors including polycrystalline silicon have high field-effect mobility, they are not suitable for being formed over a larger glass substrate.
Other than a transistor formed using silicon, a technique in which a transistor is formed using an oxide semiconductor and applied to an electronic device or an optical device has attracted attention. For example, a technique of manufacturing a transistor by using zinc oxide or In—Ga—Zn—O-based oxide as oxide semiconductor, and of using the transistor for a switching element of a pixel of a display device and the like is disclosed in Patent Document 1 and Patent Document 2.
The lattice constant of InGaO3(ZnO)m (m is a natural number) having a homologous phase is disclosed in Non-Patent Document 1.